Methods and apparatus for luminal stenting

ABSTRACT

A stent delivery device includes a first retaining polymer disposed about and retaining a self-expanding stent at a proximal end portion, a second retaining polymer disposed about and retaining the self-expanding stent at a distal end portion, a first resistance member in thermal communication with the first retaining polymer, and a second resistance member in thermal communication with the second retaining polymer. The second retaining polymer and second resistance member are configured to allow release and expansion of the distal end portion of the self-expanding stent without expansion of the proximal end portion of the self-expanding stent.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/552,105, filed on Jul. 18, 2012, which is hereby incorporated byreference in its entirety.

BACKGROUND

Lumens in the body can change in size, shape, and/or patency, and suchchanges can present complications or affect associated body functions.For example, the walls of the vasculature, particularly arterial walls,may develop pathological dilatation called an aneurysm. Aneurysms areobserved as a ballooning-out of the wall of an artery. This is a resultof the vessel wall being weakened by disease, injury or a congenitalabnormality. Aneurysms have thin, weak walls and have a tendency torupture and are often caused or made worse by high blood pressure.Aneurysms can be found in different parts of the body; the most commonbeing abdominal aortic aneurysms (AAA) and the brain or cerebralaneurysms. The mere presence of an aneurysm is not alwayslife-threatening, but they can have serious heath consequences such as astroke if one should rupture in the brain. Additionally, a rupturedaneurysm can also result in death.

Vascular devices or “occluding devices” such as stents are often used totreat patients with aneurysms. Stent and/or other occluding devices canbe implanted within the vasculature of a patient by a delivery systemsuch as a catheter. Precise and accurate positioning of these vasculardevices at a target site is often required before a stent can be safelyand effectively detached from the stent delivery system to a target sitewithin a patient's vasculature. Positioning can be a delicate processthat may require positioning and re-positioning of the stent deliverydevice prior to the detachment of the stent.

SUMMARY

In some aspects, embodiments disclosed herein relate to a stent deliverydevice comprising a first retaining polymer disposed about and retaininga proximal end portion of a self-expanding stent when the stent is in acompressed configuration, a second retaining polymer disposed about andretaining a distal end portion of the self-expanding stent in thecompressed configuration, a first resistance member in thermalcommunication with the first retaining polymer, and a second resistancemember in thermal communication with the second retaining polymer,wherein the second retaining polymer and second resistance member areconfigured to permit expansion of the distal end portion of theself-expanding stent to an expanded configuration without expansion ofthe proximal end portion of the self-expanding stent.

In some aspects, embodiments disclosed herein relate to a system forstent delivery comprising a self-expanding stent having a proximal endportion, a distal end portion, and a lumen, a push wire extendingthrough the lumen, a first retaining polymer disposed about andretaining the proximal end portion in a compressed configuration, asecond retaining polymer disposed about and retaining the distal endportion in a compressed configuration, a first resistance member inthermal communication with the first retaining polymer, and a secondresistance member in thermal communication with the second retainingpolymer, wherein the push wire is configured to deliver a current to thefirst and second resistance members, wherein each of the first andsecond retaining polymers are configured to disengage from the stent inresponse to different levels of applied current, thereby permittingexpansion of the respective proximal and distal end portions to anexpanded configuration.

In some aspects, embodiments disclosed herein relate to a method ofdelivering a stent comprising introducing a stent delivery device viacatheter to a desired treatment location in a subject; said stentdelivery device comprising a first retaining polymer disposed about andretaining a proximal end portion of a self-expanding stent when thestent is in a compressed configuration, a second retaining polymerdisposed about and retaining a distal end portion of the self-expandingstent in the compressed configuration, a first resistance member inthermal communication with the first retaining polymer, and a secondresistance member in thermal communication with the second retainingpolymer, wherein the second retaining polymer and second resistancemember are configured to permit expansion of the distal end portion ofthe self-expanding stent to an expanded configuration without expansionof the proximal end portion of the self-expanding stent, and applying acurrent to the second resistance member to release and expand the distalend portion.

In some aspects, embodiments disclosed herein relate to a method oftreating an aneurysm comprising introducing a stent delivery device viacatheter in the vicinity of an aneurysm in a subject; the stent deliverydevice comprising a first retaining polymer disposed about and retaininga self-expanding stent at a proximal end, a second retaining polymerdisposed about and retaining the self-expanding stent at a distal end, afirst resistance member in thermal communication with the firstretaining polymer, and a second resistance member in thermalcommunication with the second retaining polymer, the second retainingpolymer and second resistance member are configured to allow release anddeployment of the distal end of the self-expanding stent without releaseof the proximal end of the self-expanding stent from the first retainingpolymer; and the method further comprising applying a current to thesecond resistance member to release and deploy the distal end of theself-expanding stent.

Additional features and advantages of the subject technology will be setforth in the description below, and in part will be apparent from thedescription, or may be learned by practice of the subject technology.The advantages of the subject technology will be realized and attainedby the structure particularly pointed out in the written description andembodiments hereof as well as the appended drawings.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the subject technology.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide furtherunderstanding of the subject technology and are incorporated in andconstitute a part of this specification, illustrate aspects of thedisclosure and together with the description serve to explain theprinciples of the subject technology.

FIG. 1 is a partial cross-sectional view of an exemplary stent deliverysystem, according to one or more embodiments disclosed.

FIG. 2A shows a delivery device having resistive heating elements inthermal contact with selectively and sequentially removable first andsecond retaining polymer members. The first and second retaining polymermembers hold the stent in a longitudinally extended form against theforce of longitudinal contraction and radial expansion.

FIG. 2B shows the stent of FIG. 2A after it has been released from thedelivery device. As the stent expands radially, there is significantlongitudinal contraction.

FIG. 3A shows a system comprising the delivery device of FIG. 2Adisposed within a catheter, the device having a guidewire tolongitudinally position the delivery device.

FIG. 3B shows the system of FIG. 3A generically attached to separatepower sources for selective and separate delivery of a current to thefirst and second retaining polymer members. One source may be theguidewire, while another source may be an electrode disposed in the wallof the catheter.

FIGS. 4A and 4B show the selective removal of the distal secondretaining polymer of the device of FIG. 2A allowing selective deploymentof the self-expanding stent at the distal end. FIG. 4A shows a stentheld in place by a proximal first retaining polymer and a distal secondretaining polymer. FIG. 4B shows the deployment of the distal end of thestent after selective removal of the distal second retaining polymer.

FIGS. 5A-D show a method of employing the system of FIG. 3A at the siteof an aneurysm. FIG. 5A shows a stent delivery system with catheterdelivery of a stent held in place by a proximal first retaining polymerand a distal second retaining polymer. FIG. 5B shows the deployment ofthe distal end of the stent after selective removal of the distal secondretaining polymer, with the system still in place within the catheter,allowing for any adjustment for positioning of the stent. FIG. 5C showsthe system after removal of the delivery catheter with the distal end ofthe stent now deployed at one end the aneurysm. FIG. 5D shows the fullydeployed stent screening off the aneurysm after release of the proximalfirst polymer and removal of the guidewire.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are setforth to provide a full understanding of the subject technology. It willbe apparent, however, to one ordinarily skilled in the art that thesubject technology may be practiced without some of these specificdetails. In other instances, well-known structures and techniques havenot been shown in detail so as not to obscure the subject technology.

Described herein are various embodiments of stent delivery systemsexhibiting small cross-sections which are highly flexible. Referring toFIG. 1, illustrated is an exemplary stent delivery system 20 including astent 100 carried by a core wire 41 as arranged within an introducersheath or catheter 4. The stent 100 and the core wire 41 may becooperatively movable within the catheter 4 in order to deliver thestent 100 to a predetermined treatment site, such as an aneurysm, withinthe vasculature of a patient. Accordingly, the catheter 4 may beconfigured to be introduced and advanced through the vasculature of thepatient. The catheter 4 may be made from various thermoplastics, e.g.,PTFE, FEP, HDPE, PEEK, etc., which may optionally be lined on the innersurface of the catheter 4 or an adjacent surface with a hydrophilicmaterial such as PVP or some other plastic coating. Additionally, eithersurface may be coated with various combinations of different materials,depending upon the desired results.

The stent 100 may be characterized as a vascular occluding device and/oran embolization device, as generally known in the art. These terms arebroad terms and are intended to have their ordinary meaning and include,unless expressly otherwise stated or incompatible with the descriptionof, each of the stents and other vascular devices described herein. Insome embodiments, the stent 100 may be a self-expanding stent made oftwo or more round or ovoid wire filaments. The filaments may be formedof known flexible materials including shape memory materials, such asnitinol, platinum, and stainless steel. In some embodiments, the stent100 is fabricated from platinum/8% tungsten and 35N LT (cobalt nickelalloy, which is a low titanium version of MP35N alloy) alloy wires. Inother embodiments, one or more of the filaments can be formed of abiocompatible metal material or a biocompatible polymer.

The wire filaments may be braided into a resulting lattice-likestructure. In at least one embodiment, during braiding or winding of thestent 100, the filaments may be loosely braided using a 1-over-2-under-2system. In other embodiments, however, other methods of braiding may befollowed, without departing from the scope of the disclosure. The stent100 may exhibit a porosity configured to reduce haemodynamic flow into,for example, an aneurysm, but simultaneously allow perfusion to anadjacent branch vessel. As will be appreciated, the porosity of thestent 100 may be adjusted by “packing” the stent during deployment, asknown in the art. The ends of the stent 100 may be cut to length andtherefore remain free for radial expansion and contraction. The stent100 may exhibit a high degree of flexibility due to the materials used,the density (i.e., the porosity) of the filaments, and the fact that theends are not secured.

The flexibility of the core wire 41 allows the stent delivery system 20to bend and conform to the curvature of the vasculature as needed forpositional movement of the stent 100 within the vasculature. The corewire 41 may be made of a conventional guidewire material and have asolid cross-section. Alternatively, the core wire 41 can be formed froma hypotube. The material used for the core wire 41 can be any of theknown guidewire materials including superelastic metals or shape memoryalloys, e.g., nitinol. Alternatively, the core wire 41 can be formed ofmetals such as stainless steel.

In one or more embodiments, the stent delivery system 20 may exhibit thesame degree of flexion along its entire length. In other embodiments,however, the stent delivery system 20 can have two or more longitudinalsections, each with differing degrees of flexion/stiffness. Thedifferent degrees of flexions for the stent delivery system 20 can becreated using different materials and/or thicknesses within differentlongitudinal sections of the core wire 41. In some embodiments, theflexion of the core wire 41 can be controlled by spaced cuts (not shown)formed within the core wire 41. These cuts can be longitudinally and/orcircumferentially spaced from each other.

A tip 28 and flexible tip coil 29 may be secured to the distal end 27 ofthe delivery core wire 41. The tip 28 can be characterized as a distalsolder joint formed of a continuous end cap or cover as shown in thefigures, which securely receives a distal end of the tip coil 29.Flexion control is provided to the distal end 27 of the delivery corewire 41 by the tip coil 29. However, in an embodiment, the tip 28 can befree of the coil 29. As illustrated, the tip 28 may have anon-percutaneous, atraumatic end face. The tip coil 29 may be configuredto surround at least a portion of the core wire 41. The tip coil 29 isflexible so that it will conform to and follow the path of a vesselwithin the patient as the tip 28 is advanced along the vessel and thecore wire 41 bends to follow the tortuous path of the vasculature.

At the proximal end 107 of the stent 100, a proximal solder joint 52 andproximal marker 88 prevent or limit lateral movement of the stent 100along the length of the core wire 41 in the direction of the proximalend 107. As illustrated, the proximal end 107 of the stent 100 may beaxially-offset from the proximal marker 88 by a short distance. In otherembodiments, however, the stent 100 may shift axially duringintroduction into the vasculature of the patient and contact theproximal marker 88 which prevents or limits the stent 100 from movingalong the length of the core wire 41 away from a distally-locatedprotective coil 85 coupled to an adjacent or mid solder joint 82.

After navigating the length of the catheter 4 to the predeterminedtreatment site within the patient, the stent 100 may be deployed fromthe catheter 4 in a variety of ways. In one embodiment, the catheter 4is retracted while maintaining the position of the core wire 41 toexpose the distal end 27 of the delivery core wire 41 and the distal end102 of the stent 100. Upon exiting the catheter 4, the portion of thestent 100 that is not situated between the protective coil 85 and thecore wire 41 and that is not covered by the catheter 4 begins to expandradially. The catheter 4 may then be further retracted until enough ofthe stent 100 is exposed such that the expansion diameter of the stent100 is sufficient to engage the walls of the vessel (not shown), such asa blood vessel. Upon engaging a portion of said vessel, the stent 100may be at least partially anchored within the vessel.

The core wire 41 may then be rotated at its proximal end, which causesrotation at the distal end 27 relative to the stent 100. The rotation ofthe core wire 41 also causes twisting of the protective coil 85, whichpushes the distal end 102 of the stent 100 out from beneath theprotective coil 85 like a corkscrew. Once the distal end 102 of thestent 100 is released from the protective coil 85, it expands to engagethe walls of the vessel. The catheter 4 may then be further retracted toexpose and expand the remaining portions of the stent 100.

Those skilled in the art will readily recognize that variations of thisdeployment method are possible. For example, the catheter 4 may befurther retracted before rotating the core wire 41, such as by expandingthe proximal end 107 of the stent 100 before expanding the distal end102. Other examples of deployment variations include causing orotherwise creating variable porosity of the stent 100.

Once the entire stent 100 is expanded, the core wire 41 may then beretracted back into the catheter 4 by pulling proximally on the corewire 41 and maintaining the catheter 4 in its position. The proximaltaper of the solder joint 52 coupled to the proximal marker 88 helpsguide retraction of the core wire 41 back into the catheter 4. The corewire 41 and the catheter 4 may then be both retracted from the vesseland vasculature of the patient.

In some aspects, embodiments disclosed herein provide stent deliverydevices, as exemplified by shown in FIG. 2A, comprising a firstretaining polymer 810 disposed about and retaining a self-expandingstent 805 at a proximal end 830, a second retaining polymer 820 disposedabout and retaining the self-expanding stent at a distal end 840, afirst resistance member 815 in thermal communication with firstretaining polymer 810, and a second resistance member 825 in thermalcommunication with second retaining polymer 820. Second retainingpolymer 820 and second resistance member 825 are configured to allowrelease and deployment of distal end 840 of self-expanding stent 805without release of proximal end 830 of self-expanding stent 805 fromfirst retaining polymer 810. The heat produced, for example, viaresistive heating (also called ohmic heating) is proportional to thesquare of the current multiplied by the electrical resistance of thewire in accordance with Joule's First Law:QαI2·Rwherein Q is the heat in joules, I is the current in amperes, and R isthe resistance in ohms. Selectivity for release of distal end 840 ofself-expanding stent 805 via resistive heating may be a function of thepolymer selected in conjunction with calculations of the heat suppliedaccording to Joule's First Law. Of the many advantages of selectiverelease of one end of self-expanding stent 805 is the ability to finetune the position of self-expanding stent 805, via catheter delivery, bypulling deployed distal end 840 back into the catheter to realign thestent. In this regard, self-expanding stent 805, the catheter, or both,may be further equipped with a radio-opaque fiducial marker to guide itsplacement.

Referring again to FIG. 2A, and with reference to FIG. 2B, first andsecond retaining polymer members 810 and 820 are configured hold stent805 in place against forces inherent in self-expanding stent 805 thatprovide for self expansion and longitudinal contraction upon up releasefrom the device. In operation, release of just distal end 840 fromsecond retaining polymer member 820 may allow partial longitudinalcontraction and initial expansion of self-expanding stent 805. The exactdegree of radial expansion and/or longitudinal contraction may bemitigated by, inter alia, the presence or absence of a deliverycatheter.

In some embodiments, stent delivery devices disclosed herein may furthercomprise a push wire 850 which can be used to guide the stent deliverydevice when in use. Push wire 850 may also be used to supply therequisite current to first resistance member 815, second resistancemember 825, or both. In some embodiments, push wire 850 does not carrycurrent to either resistance member. In other embodiments, push wire 850may carry current to an electrode embedded with the wall of a deliverycatheter for subsequent delivery to either or both resistance members815 and/or 825. The distal end of push wire 850 may comprise a bluntatraumatic tip 860, as recognized by those skilled in the art.

First retaining polymer 810 and second retaining polymer 820 maycomprise any thermoplastic or thermoset material, although the skilledartisan will recognize that for good melt characteristics, firstretaining polymer 810 and second retaining polymer 820 may bebeneficially a thermoplastic. Nonetheless, thermoset materials may beemployed in devices disclosed herein. Thermoset materials may not have atrue melting point, but may become more pliable/elastic and/or maydecompose upon resistive heating, for example, to allow release atdistal end 840 or proximal end 830 of self-expanding stent 805. In thisregard, the material may be more accurately characterized by itssoftening point (Vicat softening point as described herein below). Insome embodiments, distal end 840 is a thermoplastic and proximal end 830is a thermoset material. In some embodiments, distal end 840 is athermoplastic and proximal end 830 is also a thermoplastic. In someembodiments, distal end 840 is a thermoset material and proximal end 830is a thermoplastic. In some embodiments, distal end 840 and proximal end830 are both thermoset materials.

Thermoplastic polymers may include, without limitation, acrylonitrilebutadiene styrene (ABS), acrylic-based polymers such as PMMA, celluloid,cellulose acetate, cyclic olefin copolymer (COC), ethylene-vinyl acetate(EVA), ethylene vinyl alcohol (EVOH), fluoroplastics, such as PTFE, FEP,PFA, CTFE, ECTFE, and ETFE, ionomers, KYDEX™, an acrylic/polyvinylchloride (PVC) alloy, liquid crystal polymer (LCP), polyoxymethylene(POM or acetal), polyacrylates, polyacrylonitrile (PAN oracrylonitrile), polyamide (PA or Nylon), polyamide-imide (PAI),polyaryletherketone (PAEK or Ketone), polybutadiene (PBD), polybutylene(PB), polybutylene terephthalate (PBT), polycaprolactone (PCL),polychlorotrifluoroethylene (PCTFE), polyethylene terephthalate (PET),polycyclohexylene dimethylene terephthalate (PCT), polycarbonate (PC),polyhydroxyalkanoates (PHAs), polyketone (PK), polyester, polyethylene(PE), polyetheretherketone (PEEK), polyetherketoneketone (PEKK),polyetherimide (PEI), polyethersulfone (PES), chlorinated polyethylene(CPE), polyimide (PI), polylactic acid (PLA), polymethylpentene (PMP),polyphenylene oxide (PPO), polyphenylene sulfide (PPS), polyphthalamide(PPA), polypropylene (PP), polystyrene (PS), polysulfone (PSU),polytrimethylene terephthalate (PTT), polyurethane (PU), polyvinylacetate (PVA), polyvinyl chloride (PVC), polyvinylidene chloride (PVDC),ptyrene-acrylonitrile (SAN), and combinations thereof. Any of theaforementioned thermoplastics may be combined/coextruded in anycombination of two, three, four, or more thermoplastic materials totailor to desired melting characteristics. As will be recognized by theskilled artisan, the exact selection of a thermoplastic may depend on,inter alia, the heat supplied by resistive heating of first resistancemember 815 and/or second resistance member 825, and safety factors ofthe material employed in the area where the stent is intended to bedeployed. Thermoplastic materials may be integrated into device 800 viamelt forming about distal end 840 and/or proximal end 830 ofself-expanding stent 805.

Thermoset polymers may include, without limitation, phthalic/maelic typepolyesters, vinyl esters, epoxies, phenolics, phenol-formaldehyde,cyanates, cyanate esters, polycyanurates, bismaleimides, polyimides,nadic end-capped polyimides, such as PMR-15, duroplast,urea-formaldehyde, melamine, and combinations thereof. As withthermoplastic materials, safety and the ability to release the one ofthe two stent ends may factor into the exact choice of a thermosetmaterial. Thermoset materials may be integrated with the device bystandard methods known in the art such as injection or compressionmolding, for example.

In some embodiments, second retaining polymer 820 and second resistancemember 825 are configured to allow release and deployment of distal end840 of self-expanding stent 805 without release of proximal end 830 ofself-expanding stent 805 from first retaining polymer 810. Suchselective release of distal end 840 may allow for repositioning of thestent via reversible re-entry into a delivery catheter. FIG. 3A shows anexample of device 800 disposed within a delivery catheter 970.

In some such embodiments, stent delivery devices disclosed herein may beprovided with current that is independently deliverable to firstresistance member 815 and second resistance member 825, as indicatedgenerically in FIG. 3B. FIG. 3B shows a distal power source 870configured to be in electronic communication with second resistancemember 825 and a proximal power source 875 configured to be inelectronic communication with first resistance member 815. In someembodiments, distal power source 870 may be provided by an electrodeembedded in the wall of the catheter. In some embodiments, distal powersource 870 may be provided by splitting of a wire bundle off guidewire850. In some embodiments, differential delivery of current may beachieved, for example, via delivery to one resistance member via pushwire 850 and the other resistance member via, for example, an electrodedisposed on a wall of delivery catheter 970. Thus, for example, releaseof second retaining polymer 820 may be selectively achieved by supplyingdelivery catheter 970 with a current to resistively heat secondresistance member 825, while release of first retaining polymer 810 maybe achieved via current delivery via push wire 850 which may resistivelyheat first resistance member 815. In such a configuration, it may bebeneficial to electrically isolate second resistance member 825 frompush wire 850.

In some embodiments, push wire 850 may comprise a plurality of wires ina bundle wherein a first portion of the bundle of wires may selectivelydeliver a current to second resistance member 825 and a second portionof the bundle of wires may selectively deliver a current to firstresistance member 815. In some embodiments, selective delivery ofcurrent to first resistance member 815 and second resistance member 825may be achieved via separately positioned electrodes within the wall ofa delivery catheter 970. In some embodiments, a single electrode withindelivery catheter 970 may be positioned to provide a current to secondresistance member 825, and after properly aligning the stent intoposition, the same electrode may be re-aligned to deliver a current tofirst resistance member 815. In some embodiments, a single currentsource may be split to deliver a greater current to second resistancemember 825. In such a situation, when the resistance of secondresistance member 825 and first resistance member 815 are the same, moreheat will be generated at second resistance member 825, according toJoule's First law.

In some embodiments, stent delivery devices disclosed herein may have athickness of the second retaining polymer that is less than thethickness of first retaining polymer such that application of a current,including the same current source, to the first and second resistancemembers, 815 and 825, respectively, results in selective rapid meltingof the second retaining polymer 820. In some such embodiments, thethickness of the polymer alone may provide the requisite removalselectivity and the first retaining polymer 810 and second retainingpolymer 820 may comprise the same material. In other embodiments, thethickness of second retaining polymer 820 may be less than the thicknessof first retaining polymer 810 and the materials making up the tworetaining polymers may further differ in melting points. In such aconfiguration, the differences in melting point and thickness of thematerial may synergistically provide the requisite selectively forremoving second retaining polymer 820 from distal end 840. Where thematerials employed may have differing melt characteristics, by way ofdiffering melting points, differing thickness, or combinations thereof,the resistance of first resistance member 815 and second resistancemember 825, may be in a range from about 50 ohms to about 20 megaohms,with an applied current in a range from about 10 microamps to about 20amps.

In some embodiments, stent delivery devices disclosed herein may have aresistance of second resistance member 825 that is higher than theresistance of first resistance member 815. Thus, for example, a singlecurrent may be supplied to both first resistance member 815 and secondresistance member 825 via electrical contact with push wire 850, whichis itself supplied with a current. Thus, the resistive heating suppliedby second resistance member 825 to second retaining polymer 820 may begreater than the resistive heating supplied by first resistance member815 to first retaining polymer 810. Thus, by judicious choice of meltingpoint (or softening point) of the polymer material of first retainingpolymer 810 and second retaining polymer 820, a specific current andresistance may be applied to first resistance member 815 and/or secondresistance member 825 to effect the release of proximal end 830 ordistal end 840 with the desired selectivity. As used herein, the term“melting point” generally refers to a thermoplastic polymer andrepresents the temperature at which the solid phase and liquid phase ofthe polymer coexist in equilibrium. As used herein, the term “softeningpoint” may be used to generally refer to the relaxation of a polymer,such as a thermoset, which does not have a true melting point, butnonetheless becomes more pliable with heating. In some such embodiments,the “softening point” may be the softening point as recognized by thoseskilled in the art of plastics. Standards to determine Vicat softeningpoint include, but are not limited to, ASTM D 1525 and ISO 306.

In an ohmic heating regime employing second resistive member 825 havinga resistance higher than first resistance member 815, the resistance ofthe second resistance member may be in a range from about 50 ohms toabout 20 megaohms, with an applied current in a range from about 10microamps to about 20 amps. By way of example, release of distal end 840may be achieved with a current of 10 microamps, and resistance of 20megaohms, employing a polymer material for second retaining polymer suchas low-melting polymers and low-melting polymer blends.

In some embodiments, stent delivery devices 800 disclosed herein mayprovide first retaining polymer 810 and second retaining polymer 820having different melting points. In some embodiments, under theoperating conditions for deployment of distal end 840 and proximal end830, the melting points of the retaining polymer may be in a range fromabout 40° C. to about 100° C.

In some aspects, embodiments disclosed herein provide a system 900, asshown in FIG. 3A, for stent delivery comprising a catheter 970, a stentdeliver device 800 comprising a first retaining polymer 810 disposedabout and retaining a self-expanding stent 805 at a proximal end 830, asecond retaining polymer 820 disposed about and retaining theself-expanding stent 805 at a distal end 840, a first resistance member815 in thermal communication with first retaining polymer 810, and asecond resistance member 825 in thermal communication with secondretaining polymer 820, second retaining polymer 820 and secondresistance member 825 are configured to allow release and deployment ofdistal end 840 of self-expanding stent 805 without release of proximalend 830 of self-expanding stent 805 from first retaining polymer 810,and system 900 further comprising a push wire 850, extending through thelumen of the self-expanding stent 805, push wire 850 being capable ofdelivering a current to first resistance member 815, second resistancemember 825, or combinations thereof.

In some embodiments, system 900 disclosed herein may deploy distal end840 of self-expanding stent 805 in a reversible manner by pulling theself-expanding stent 805 back into catheter 970, even in the event wherethe catheter has been initially removed from the system duringdeployment. By drawing released distal end 840 back into catheter 970allows for repositioning of the stent. In some embodiments, system 900disclosed herein may employ a current that is independently deliverableto first resistance member 815 and second resistance member 825. Asdescribed above, this may be achieved by delivery of current to pushwire 850, one or more electrodes disposed within the wall of catheter970, or combinations thereof.

In some embodiments, first retaining polymer 810 and second retainingpolymer 820 may be disposed about self-expanding stent 805 in a mannersuch that self-expanding stent 805 is under a tension and elongatedrelative to the fully deployed state. Push wire 850 may also provide anattachment point at each end of self-expanding stent 805 to which firstretaining polymer 810 and second retaining polymer 820 are attached andheld in apart prior to deployment. Referring to FIGS. 4A and 4B, thereis shown device 800 before (4A) and after (4B) release of distal end 840from second retaining polymer 820. Note that, in use, delivery catheter970 may or may not be present during deployment of distal end 840. Thatis, delivery catheter 970 may be present at the site of released distalend 840 or not. In some embodiments, delivery catheter 970 may be absentat the site of released distal end 840, but still present over at leasta portion of device 800. In other embodiments, delivery catheter may becompletely removed from device 800 during deployment, as shown in FIGS.4A and 4B. After release of distal end 840, self-expanding stent 805 maycontract longitudinally while also expanding to greater diameter, asshown in FIG. 4B. Likewise the melting of second retaining polymer 820may be accompanied by curling or shrinking of the polymer material toaid in release of distal end 840. In some embodiments, system 900 mayinclude a stent 805 having fiducial marker that indicates the successfulrelease of the distal end 840 of self-expanding stent 805.

Further in accordance with embodiments describing device 800 above,system 900 may employ a thickness of second retaining polymer 820 thatis less than a thickness of first retaining polymer 810 such thatapplication of a current to the first and second resistance members, 815and 825, respectively, results in selective rapid melting of secondretaining polymer 820 selectively over first retaining polymer 810. Insome embodiments, the thickness of first retaining polymer 810 may be ina range from about 10 microns to about 2 mm, including all values inbetween and fractions thereof. In some embodiments, the thickness ofsecond retaining polymer 820 may be in a range from about 10 microns toabout 2 mm, including all values in between and fractions thereof. Insome embodiments, system 900 employing selective release of distal end840 on the basis of having a thickness differential may be characterizedby a difference in thickness of first retaining polymer 810 and secondretaining polymer 820 in a range from about 1 micorn to about 2 mm.

Further in accordance with embodiments describing device 800, system 900may also provide the first retaining polymer and second retainingpolymer having different melting points. In some embodiments, system 900having differing melting point retaining polymers, a differential inmelting point between the two polymers may be in a range from about 5°C. to about 40° C., including any value in between or fractions thereof.Consistent with embodiments disclosed herein, combinations of meltingpoint differentials and polymer thicknesses may be employed to provide asystem capable of selective deployment of distal end 840.

In some embodiments, system 900 may provide a resistance of secondresistance member 825 that is higher than the resistance of firstresistance member 815, as described above. The resistance members may bewire or ribbon in straight or coiled form. In some embodiments,differential resistance may be provided by providing differentmaterials. In some embodiments, first and second resistance members 815,825 may comprise any material known in the art including, withoutlimitation, KANTHAL™ (FeCrAl), nichrome 80/20, cupronickel (CuNi)alloys, and the like. In some embodiments, first and/or secondresistance members 815, 825 may be in electrical communication with pushwire 850. In some such embodiments, first and/or second resistancemembers 815, 825 may be attached to push wire 850 via a solder weld, forexample.

Finally, in some embodiments, system 900 may further comprise one ormore power sources for delivering a current to first resistance member815 and second resistance member 825. The power source may delivercurrent in a constant manner or may be pulsed. In some embodiments, thepower source may be beneficially in electronic communication with distalend 840 to provide a signal to terminate delivery of current to thesystem to assure that proximal end 830 remains attached toself-expanding stent 805 to allow for any necessary readjustment of thepositioning of the stent 805. Such repositioning may be needed, forexample, due to the concomitant contraction of self-expanding stent 805upon release of distal end 840. In some embodiments, the signal toterminate delivery of current may include detection of a change inposition of a fiducial marker on self-expanding stent 805.

In some aspects, embodiments disclosed herein provide methods ofdelivering a stent comprising: introducing a stent delivery device viacatheter to a desired treatment location in a subject, the stentdelivery device comprising a first retaining polymer disposed about andretaining a self-expanding stent at a proximal end, a second retainingpolymer disposed about and retaining the self-expanding stent at adistal end, a first resistance member in thermal communication with thefirst retaining polymer, and a second resistance member in thermalcommunication with the second retaining polymer, wherein the secondretaining polymer and second resistance member are configured to allowrelease and deployment of the distal end of the self-expanding stentwithout release of the proximal end of the self-expanding stent from thefirst retaining polymer, and the method further comprising applying acurrent to the second resistance member to release and deploy the distalend of the self-expanding stent.

Referring now to FIGS. 5A-D, there is shown a method 1000 for deliveringa self-expanding stent 805. At step 1010, FIG. 5A, device 800 isintroduced, via catheter 970 of system 900, to a desired treatmentlocation 999 in a subject. At step 1020, FIG. 5B, distal end 840 isreleased from second retaining polymer 820. In some embodiments, thisrelease is conducted as shown in FIG. 5B, in the presence of catheter970. In other embodiments, release of distal end 840 may be conducted inthe absence of delivery catheter 970 to deploy directly the distal endtreatment location 999. In some embodiments, methods of delivering astent disclosed herein may optionally comprise adjusting deployed distalend 840 of self-expanding stent 805 by pulling the self-expanding stent805 back into the catheter 970, if not within the catheter duringdeployment. After readjustment of released distal end 840 the cathetermay be removed to redeploy the stent as shown in step 1030, FIG. 5C. Atthis point, released distal end 840 may be expanded and in contact witha portion just beyond the distal end of treatment location 999. Becausefirst retaining polymer 810 is still attached to the stent, the operatorhas the continuing option to reintroduce delivery catheter 970 to makeany further positioning adjustments to self-expanding stent 805 asnecessary. At this stage step 1040, FIG. 5D, may be performed to releaseproximal end 830 of the self-expanding stent 805 by supplying a currentto the first resistance member 815. Again, while FIG. 5C shows therelease absent catheter 970, one skilled in the art will recognize thatrelease of proximal end 830 may be performed while delivery catheter 970is still present, as in FIG. 5B. The fully deployed stent 805 in step1040, FIG. 5D, may be contracted longitudinally relative to stent 805still disposed within device 800.

Methods of deploying self-expanding stent 805 may include selectiverelease of distal end 840 consistent with embodiments disclosed herein.Thus, in some embodiments, methods of delivering a stent disclosedherein may provide a current that is independently deliverable to thefirst resistive member and second resistive member. Further, in someembodiments, methods of delivering a stent disclosed herein may providea thickness of the second retaining polymer that is less than athickness of first retaining polymer such that application of a currentto the first and second resistance members results in selective rapidmelting of the second retaining polymer. In yet further embodiments,methods of delivering a stent disclosed herein may provide theresistance of the second resistance member that is higher than theresistance of the first resistance member. In still further embodiments,methods of delivering a stent disclosed herein may provide the firstretaining polymer and second retaining polymer have different meltingpoints. Any of the foregoing features may be used in any combination toeffect selective release of distal end 840.

In some aspects, embodiments disclosed herein provide a method oftreating an aneurysm, which is also represented by FIGS. 5A-D,comprising introducing a stent delivery device via catheter in thevicinity of an aneurysm in a subject; said stent delivery devicecomprising a first retaining polymer disposed about and retaining aself-expanding stent at a proximal end, a second retaining polymerdisposed about and retaining the self-expanding stent at a distal end, afirst resistance member in thermal communication with the firstretaining polymer, and, a second resistance member in thermalcommunication with the second retaining polymer, wherein the secondretaining polymer and second resistance member are configured to allowrelease and deployment of the distal end of the self-expanding stentwithout release of the proximal end of the self-expanding stent from thefirst retaining polymer, and the method further comprising applying acurrent to the second resistance member to release and deploy the distalend of the self-expanding stent.

Consistent with methods of delivering a stent to a desired treatmentlocation, in some embodiments, methods of treating an aneurysm mayfurther comprise adjusting the deployed distal end of the self-expandingstent by pulling the self-expanding stent into the catheter. In yetfurther embodiments, methods of treating an aneurysm may furthercomprise removing the catheter to redeploy the stent. In still furtherembodiments, methods of treating an aneurysm may further comprisedeploying the proximal end of the self-expanding stent by supplying acurrent to the first resistance member.

Methods of deploying self-expanding stent 805 to treat an aneurysm mayinclude selective release of distal end 840 consistent with embodimentsdisclosed herein. Thus, in some embodiments, methods of treating ananeurysm may provide a current that is independently deliverable to thefirst resistance member 815 and second resistance member 825. In someembodiments, methods of treating an aneurysm may provide a thickness ofsecond retaining polymer 820 that is less than a thickness of firstretaining polymer 810 such that application of a current to the firstand second resistance members results in selective rapid melting of thesecond retaining polymer 820. In some embodiments, methods of treatingan aneurysm may provide the resistance of second resistance member 825that is higher than the resistance of the first resistance member 815.In some embodiments, methods of treating an aneurysm may provide firstretaining polymer 810 and second retaining polymer 820 having differentmelting points. Any of the foregoing features may be used in anycombination to effect selective release of distal end 840 to treat ananeurysm.

In some embodiments, methods of deploying self-expanding stent to treatan aneurysm may further include introducing a stent having a drugcoating. In some such embodiments, the drug coating may release a drugin a controlled manner to block cell proliferation and reduce or preventfibrosis and clotting associated with restenosis. In some embodiments,methods of deploying a self-expanding stent to treat an aneurysm mayfurther include introducing a treatment agent directly into the stentedaneurysm.

The apparatus and methods discussed herein are not limited to thedeployment and use of an occluding device or stent within the vascularsystem but may include any number of further treatment applications.Other treatment sites may include areas or regions of the body such asorgan bodies. Modification of each of the above-described apparatus andmethods for carrying out the subject technology, and variations ofaspects of the disclosure that are apparent to those of skill in the artare intended to be within the scope of the claims. Furthermore, noelement, component, or method step is intended to be dedicated to thepublic regardless of whether the element, component, or method step isexplicitly recited in the claims.

Although the detailed description contains many specifics, these shouldnot be construed as limiting the scope of the subject technology butmerely as illustrating different examples and aspects of the subjecttechnology. It should be appreciated that the scope of the subjecttechnology includes other embodiments not discussed in detail above.Various other modifications, changes and variations which will beapparent to those skilled in the art may be made in the arrangement,operation and details of the method and apparatus of the subjecttechnology disclosed herein without departing from the spirit and scopeof the subject technology as defined in the appended claims. Therefore,the scope of the subject technology should be determined by the appendedclaims and their legal equivalents. Furthermore, no element, componentor method step is intended to be dedicated to the public regardless ofwhether the element, component or method step is explicitly recited inthe claims. Underlined and/or italicized headings and subheadings areused for convenience only, do not limit the subject technology, and arenot referred to in connection with the interpretation of the descriptionof the subject technology. In the claims and description, unlessotherwise expressed, reference to an element in the singular is notintended to mean “one and only one” unless explicitly stated, but ratheris meant to mean “one or more.” In addition, it is not necessary for adevice or method to address every problem that is solvable by differentembodiments of the disclosure in order to be encompassed by the claims.

What is claimed is:
 1. A system for stent delivery, the systemcomprising: a self-expanding stent having a proximal end portion, adistal end portion, and a lumen; a push wire extending through thelumen; a first retaining polymer (a) in direct contact with the pushwire and (b) disposed about and retaining the proximal end portion in acompressed configuration; a second retaining polymer (a) in directcontact with the push wire and (b) disposed about and retaining thedistal end portion in a compressed configuration; a first resistancemember in thermal communication with the first retaining polymer; and asecond resistance member in thermal communication with the secondretaining polymer; wherein the second retaining polymer is releasablefrom the stent independently of release of the first retaining polymerfrom the stent.
 2. The system of claim 1, wherein the distal end portioncan be compressed, after expanding from the compressed configuration toan expanded configuration, by pulling the distal end portion into acatheter.
 3. The system of claim 1, wherein the first retaining polymeris configured to disengage from the stent in response to a first levelof applied current, and the second retaining polymer is configured todisengage from the stent in response to a second level of appliedcurrent, the second level being different from the first level.
 4. Thesystem of claim 3, wherein the applied current is independentlydeliverable to the first resistance member and the second resistancemember.
 5. The system of claim 1, wherein a thickness of the secondretaining polymer is less than a thickness of the first retainingpolymer, such that application of a current to the first resistancemember and the second resistance member results in severance of thesecond retaining polymer prior to severance of the first retainingpolymer.
 6. The system of claim 1, wherein an electrical resistance ofthe second resistance member is higher than an electrical resistance ofthe first resistance member.
 7. The system of claim 1, wherein the firstretaining polymer and the second retaining polymer have differentmelting points.
 8. The system of claim 1, wherein each of the firstretaining polymer and the second retaining polymer is configured toremain in direct contact with the push wire after disengagement from thestent.
 9. A method of delivering a stent, the method comprising:introducing a stent delivery device via a catheter to a desiredtreatment location in a subject, the stent delivery device comprising: afirst retaining polymer (a) in direct contact with a push wire and (b)disposed about and retaining a proximal end portion of a self-expandingstent when the stent is in a compressed configuration; a secondretaining polymer (a) in direct contact with the push wire and (b)disposed about and retaining a distal end portion of the self-expandingstent in the compressed configuration; a first resistance member inthermal communication with the first retaining polymer; and a secondresistance member in thermal communication with the second retainingpolymer; wherein the second retaining polymer and the second resistancemember are configured to permit expansion of the distal end portion ofthe self-expanding stent to an expanded configuration without expansionof the proximal end portion of the self-expanding stent; applying acurrent to the second resistance member to release and expand the distalend portion.
 10. The method of claim 9, further comprising compressingthe expanded distal end portion of the self-expanding stent by pullingthe self-expanding stent into the catheter.
 11. The method of claim 10,further comprising withdrawing the catheter relative to the stent tore-expand the stent.
 12. The method of claim 9, further comprisingexpanding the proximal end of the self-expanding stent by supplying acurrent to the first resistance member.
 13. The method of claim 9,wherein a current is independently deliverable to the first resistancemember and the second resistance member.
 14. The method of claim 9,wherein a thickness of the second retaining polymer is less than athickness of the first retaining polymer, such that application of asame current to the first resistance member and the second resistancemember results in severance of the second retaining polymer beforeseverance of the first retaining polymer.
 15. The method of claim 9,wherein an electrical resistance of the second resistance member isgreater than an electrical resistance of the first resistance member.16. The method of claim 9, wherein the first retaining polymer and thesecond retaining polymer have different melting points.
 17. The methodof claim 9, wherein the desired treatment location comprises ananeurysm.
 18. The method of claim 9, wherein the second retainingpolymer is in direct contact with the push wire after release from thedistal end portion.